Luo Mingyu advanced to the Qi Manifestation Realm during foreplay, when her Dark Phoenix Extreme Yin physique awakened. She then was able to start utilizing her Spiritual Qi Soul to chant and circulate the Dual Extremes Infinite Union Art almost immediately after, freeing up her mind to focus on the sensations and pleasure, on the act itself. Dao cultivators were naturally more proficient in using their Spiritual Qi Soul as a separate consciousness for such tasks, and she was a brilliant one so it took her almost no time to learn and use it despite only being able to conjure it for the first time since she just advanced to the realm in which it was possible to do.
As they were using the same dual cultivation technique now, the cultivation happened in the middle of the act for both. Their Yin and Yang Qi invigorated each other and facilitated each other's progress.